Breastfeeding over two years is associated with longer birth intervals, but not measures of growth or health, among children in Kilimanjaro, TZ

After Theranos: Using point-of-care testing to advance measures of health biomarkers in human biology research

OBJECTIVES

The rise and fall of the health technology startup Theranos is emblematic of the promise and peril of point-of-care testing (POCT). Instruments that deliver immediate results from minimally invasive samples at the location of collection can provide powerful tools to deliver health data in clinical and public health contexts. Yet, POCT availability is driven largely by market interests, which limits the development of inexpensive tests for diverse health conditions that can be used in resource-limited settings. These constraints, combined with complex regulatory hurdles and substantial ethical challenges, have contributed to the underutilization of POCT in human biology research.

METHODS

We evaluate current POCT capabilities and limitations, discuss promising applications for POCT devices in resource-limited settings, and discuss the future of POCT.

RESULTS

As evidenced by publication trends, POCT platforms have rapidly advanced in recent years, gaining traction among clinicians and health researchers. We highlight POCT devices of potential interest to population-based researchers and present specific examples of POCT applications in human biology research.

CONCLUSIONS

Several barriers can limit POCT applications, including cost, lack of regulatory approval for non-clinical use, requirements for expensive equipment, and the dearth of validation in remote field conditions. Despite these issues, we see immense potential for emerging POCT technology capable of analyzing new sample types and used in conjunction with increasingly common technology (e.g., smart phones). We argue that the fallout from Theranos may ultimately provide an opportunity to advance POCT, leading to more ethical data collection and novel opportunities in human biology research.

Breastfeeding Beyond 12 Months: Is There Evidence for Health Impacts?

Because breastfeeding provides optimal nutrition and other benefits for infants (e.g., lower risk of infectious disease) and benefits for mothers (e.g., less postpartum bleeding), health organizations recommend that healthy infants be exclusively breastfed for 4 to 6 months in the United States and 6 months internationally. Recommendations related to how long breastfeeding should continue, however, are inconsistent. The objective of this article is to review the literature related to evidence for benefits of breastfeeding beyond 1 year for mothers and infants. In summary, human milk represents a good source of nutrients and immune components beyond 1 year. Some studies point toward lower infant mortality in undernourished children breastfed for >1 year, and prolonged breastfeeding increases interbirth intervals. Data on other outcomes (e.g., growth, diarrhea, obesity, and maternal weight loss) are inconsistent, often lacking sufficient control for confounding variables. There is a substantial need for rigorous, prospective, mixed-methods, cross-cultural research on this topic. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Teeth reveal juvenile diet, health and neurotoxicant exposure retrospectively: What biological rhythms and chemical records tell us

Integrated developmental and elemental information in teeth provide a unique framework for documenting breastfeeding histories, physiological disruptions, and neurotoxicant exposure in humans and our primate relatives, including ancient hominins. Here we detail our method for detecting the consumption of mothers' milk and exploring health history through the use of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) mapping of sectioned nonhuman primate teeth. Calcium-normalized barium and lead concentrations in tooth enamel and dentine may reflect milk and formula consumption with minimal modification during subsequent tooth mineralization, particularly in dentine. However, skeletal resorption during severe illness, and bioavailable metals in nonmilk foods, can complicate interpretations of nursing behavior. We show that explorations of the patterning of multiple elements may aid in the distinction of these important etiologies. Targeted studies of skeletal chemistry, gastrointestinal maturation, and the dietary bioavailability of metals are needed to optimize these unique records of human health and behavior.

Intergenerational effects of early adversity on survival in wild baboons

Early life adversity can affect an individual's health, survival, and fertility for many years after the adverse experience. Whether early life adversity also imposes intergenerational effects on the exposed individual's offspring is not well understood. We fill this gap by leveraging prospective, longitudinal data on a wild, long-lived primate. We find that juveniles whose mothers experienced early life adversity exhibit high mortality before age 4, independent of the juvenile's own experience of early adversity. These juveniles often preceded their mothers in death by 1 to 2 years, indicating that high adversity females decline in their ability to raise offspring near the end of life. While we cannot exclude direct effects of a parent's environment on offspring quality (e.g., inherited epigenetic changes), our results are completely consistent with a classic parental effect, in which the environment experienced by a parent affects its future phenotype and therefore its offspring's phenotype.

Shifting Climates, Foods, and Diseases: The Human Microbiome through Evolution

Human evolution has been punctuated by climate anomalies, structuring environments, deadly infections, and altering landscapes. How well humans adapted to these new circumstances had direct effects on fitness and survival. Here, how the gut microbiome could have contributed to human evolutionary success through contributions to host nutritional buffering and infectious disease resistance is reviewed. How changes in human genetics, diet, disease exposure, and social environments almost certainly altered microbial community composition is also explored. Emerging research points to the microbiome as a key player in host responses to environmental change. Therefore, the reciprocal interactions between humans and their microbes are likely to have shaped human patterns of local adaptation throughout our shared evolutionary history. Recent alterations in human lifestyle, however, are altering human microbiomes in unprecedented ways. The consequences of interrupted host-microbe relationships for human adaptive potential in the future are unknown.

Parental investment in Tibetan populations does not reflect stated cultural norms

In this paper, we examined both stated norms of sex preference and actual sex-biases in parental investment in a Tibetan pastoralist society. We collected detailed demographic data on infant mortality, infant feeding, the length of interbirth intervals, and a decision when giving gifts, to examine sex-biased parental investment. Our results indicate a mismatch between self-reported son preference and measures of actual parental investment that favor daughters. We interpret this female-biased parental investment as a possible response to daughters generating more economic resources. However, the stated sex preferences of both sexes reflect cultural norms that appear to have remained unchanged over a long period, which may reflect the importance of male roles in the past. Our behavioral measures of parental investment are those most likely to be in the control of women (such as breastfeeding and interbirth interval), so this mismatch between stated and actual investment may be especially true of women.

Modernizing Evolutionary Anthropology : Introduction to the Special Issue

Evolutionary anthropology has traditionally focused on the study of small-scale, largely self-sufficient societies. The increasing rarity of these societies underscores the importance of such research yet also suggests the need to understand the processes by which such societies are being lost-what we call "modernization"-and the effects of these processes on human behavior and biology. In this article, we discuss recent efforts by evolutionary anthropologists to incorporate modernization into their research and the challenges and rewards that follow. Advantages include that these studies allow for explicit testing of hypotheses that explore how behavior and biology change in conjunction with changes in social, economic, and ecological factors. In addition, modernization often provides a source of "natural experiments" since it may proceed in a piecemeal fashion through a population. Challenges arise, however, in association with reduced variability in fitness proxies such as fertility, and with the increasing use of relatively novel methodologies in evolutionary anthropology, such as the analysis of secondary data. Confronting these challenges will require careful consideration but will lead to an improved understanding of humanity. We conclude that the study of modernization offers the prospect of developing a richer evolutionary anthropology, by encompassing ultimate and proximate explanations for behavior expressed across the full range of human societies.

Cortisol in Neonatal Mother's Milk Predicts Later Infant Social and Cognitive Functioning in Rhesus Monkeys

Milk provides not only the building blocks for somatic development but also the hormonal signals that contribute to the biopsychological organization of the infant. Among mammals, glucocorticoids (GCs) in mother's milk have been associated with infant temperament. This study extended prior work to investigate rhesus monkey (Macaca mulatta) mother-infant dyads (N = 34) from birth through 8 months postpartum. Regression analysis revealed that cortisol concentrations in milk during the neonatal period predicted impulsivity on a cognitive task, but not global social behaviors, months later. During this time period, sex-differentiated social behavior emerged. For female infants, milk cortisol concentrations predicted total frequency of play. Collectively, these findings support and extend the "lactational programming" hypothesis on the impact of maternal-origin hormones ingested via milk.

Inter-individual variation in weaning among rhesus macaques (Macaca mulatta): Serum stable isotope indicators of suckling duration and lactation

Weaning is a transition in early development with major implications for infant survival and well-being, and for maternal lifetime reproductive success. The particular strategy a primate mother adopts in rearing her offspring represents a negotiation between her ability to invest and her need to invest, and can be considered adaptive and influenced by biological and social factors. Any investigation into how and why maternal weaning strategies differ among non-human primates is limited by the precision of the measurement tool used to assess infants' weaning ages. Stable carbon and nitrogen isotope analysis of soft tissues (e.g., hair, nails, feces, urine, blood) offers an objective means of monitoring the weaning status of infants. In this study, we assess stable isotope ratios in blood serum from 14 captive rhesus macaque dyads (Macaca mulatta) at infant ages 2, 5, 6, 7, 8, and 10 months to estimate the timing of weaning events. Male infants wean earlier than female infants. Infants with the lowest birth weights wean latest. Most infants wean upon reaching 2.5 times their birth weights, sooner than when weaning elsewhere has been predicted for captive cercopithecine primates. The longest weaning periods (ca. 10 months) are observed among infants of small mothers. The shortest weaning period, between 2 and 5 months, was among the lowest ranking dyad. Parity and mothers' ages had no discernible effect on the timing of weaning events. The stable carbon and nitrogen isotope values of dams during lactation are significantly different than those of a non-lactating adult female outgroup, raising questions about the suitability and selection of adult comparative baselines in studies where lactating mothers cannot be sampled longitudinally (e.g., bioarchaeology; paleontology). Am. J. Primatol. 78:1113-1134, 2016. © 2015 Wiley Periodicals, Inc.